20
Static Electricity
1. How many excess electrons are on a sphere
with a charge of 9.20 1017 C?
2. Two charges, q1 and q2, are separated by a
distance, d, and exert a force, F, on each other.
Identify what new force will exist if
a. q1 is doubled and q2 is cut in half.
b. q1 is tripled and q2 is doubled.
7. A positive charge of 3.4 107 C exerts a
repulsive force of 9.0 N on a second charge
4.0 cm away. Determine the second charge.
8. An attractive force of 0.87 N exists between a
positive charge of 5.0 C and a negative
charge of 1.5 C. What is the distance
between the charges?
c. q2 is cut in half and d is tripled.
3. An electric force of 0.030 N acts between two
charges which are 7.2 cm apart. Calculate the
force acting between the charges if the
distance between them is reduced to 1.5 cm.
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4. Two negative charges of 24 C each are
separated by 6.0 cm. What force exists
between the charges?
5. Two charged spheres are separated by
315 mm. What is the force between them if
the charge on one sphere is 9.6 107 C
and the charge on the other sphere is
2.2 105 C?
6. Determine the electrostatic force of attraction
between a proton and an electron that are
separated by 7.5 108 m.
9. Two identical point charges exert a repulsive
force of 6.0 103 N when separated by a
distance of 6.5 cm. Calculate the charge of
each.
10. Two positively charged spheres, A and B, are
separated by 0.25 m. The charge on sphere A
is one third the charge on sphere B. Find the
charge on each sphere if the force of repulsion
is 125 N.
11. Three particles are placed in a straight line.
The left particle has a charge of
2.0 105 C, the middle particle has a
charge of 4.0 106 C, and the
right particle has a charge of 3.0 105 C.
The left particle is 56 mm from the middle
particle and the right particle is 42 mm from
the middle particle. Find the net force on the
left particle.
12. A positive charge of 23 C is 15 cm directly
north of a positive charge of 38 C. A third
positive charge of 71 C is 45 cm directly
west of the 38-C charge. Determine the net
force on the 38-C charge.
Physics: Principles and Problems
Supplemental Problems • Chapter 20
37